National quota legislation is theoretically unrivaled in its ability to substantially increase the number of women legislators elected. However, not all legislation is equally effective in achieving this goal. To improve scholarly understanding of the effect of quota legislation on the election of women, this study takes advantage of a unique quasi-experiment provided by Costa Rica, which over the past ten years employed three distinct forms of quota legislation. Evidence suggests that to achieve optimal effectiveness, quota legislation must require political parties to place a minimum percentage of women on their lists, as well as mandate these placements be in electable positions.